首页|Fluid overpressure assessment in the Berkine basin and its consequences for wellbore stability and water table contamination
Fluid overpressure assessment in the Berkine basin and its consequences for wellbore stability and water table contamination
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NSTL
Springer Nature
Several water contamination accidents have been reported in the Kebili, Nefta and Hassi Messaoud regions situated in the Saharan Platform. Two major ecological disasters in Jemna and Hassi Berkaoui, which are parts of the same region, were investigated and well documented. In this work, an evaluation of water contamination risks was conducted, taking into account the pore pressure profile. The objectives were firstly to identify the potential overpressure dangers, and then to propose adequate solutions or recommendations to reduce the accident risks. The formation pressure profile in the Berkine basin was characterized by calculation and modelling methods based on logging data and drilling parameters. The used software computed the pore pressure using the d-exponent and sonic Eaton's method. Also, accurate local formation pressure surveys were used to calibrate and validate the results achieved at different control points. As a result, five overpressure intervals in the Berkine basin were highlighted that affect the wellbore stability and cause a potential risk of reservoir fluid exchange. The overpressure intervals are hosted in evaporite series of the Late Cretaceous, Early Jurassic-Late Triassic and Devonian intervals. It was concluded that the environmentally sensitive water tables in the Berkine basin are the Complex Terminal hosted in Tertiary sands to Senonian carbonates and the Continental Intercalaire aquifer hosted in Barremian and Albian sandstones. Both water tables are widely used in Saharan oases, contain good-quality water resources and have different pressure amplitudes. Nevertheless, pore pressure studies confirm that these aquifers exhibit a risk of high contamination by oil exploration activities. Based on the resulting pressure profile and the actual wellbore weak points, the source of danger was identified and a new well architecture and exhaustive cement bond evaluation were recommended for sustainable water-table protection and wellbore integrity.
Pore pressureOverpressureDrilling safetyBerkine basinCI and CT water tables
Saadaoui, Ali、Hadji, Riheb、Adouani, Samah、Ahmadi, Riadh、Laaouar, Mohamed Salah
NSTL
Springer Nature
